Pinpoint Test E: LFC 53/DTC B1892 - Air Bag Tone Warning Indicator Circuit Failure

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough Inspection and Verification before proceeding with the Pinpoint Test.

E1 CHECK FOR A HARD OR INTERMITTENT DTC
WARNING: Restraint system diagnostic tools are for service only. Tools must be removed prior to operating the vehicle over the road. Failure to remove restraint system diagnostic tools could result in injury and possible violation of vehicle safety standards.

WARNING: Do not handle, move or change the original horizontal mounting position of the restraints control module (RCM) while the RCM is connected and the ignition switch is ON. Failure to follow these instructions may result in the inadvertent deployment of the safety canopy and risk of personal injury.

WARNING: Never probe the connectors on the air bag module. Doing so can result in air bag deployment, which can result in personal injury.

WARNING: The safety belt pretensioner is a pyrotechnic device. Always wear safety glasses when repairing an air bag equipped vehicle and when handling a safety belt buckle pretensioner or safety belt retractor pretensioner. Never probe a pretensioner electrical connector. Doing so could result in pretensioner or air bag deployment and could result in personal injury.

WARNING: Never probe the electrical connector on a safety canopy module. Doing so can result in safety canopy deployment.

NOTE: After diagnosing or repairing a supplemental restraint system (SRS), the restraint system diagnostic tools must be removed before operating the vehicle over the road.

NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
- Enter the following diagnostic mode on the diagnostic tool: Retrieve Continuous DTCs.
- Enter the following diagnostic mode on the diagnostic tool: On-Demand Self Test.
- Was DTC B1892 retrieved during the on-demand self test?
- Yes : This is a hard fault. The fault condition is still present. This fault cannot be cleared until it is corrected and the DTC is no longer retrieved during the on-demand self test. GO to E2.
- No : This is an intermittent fault. The fault condition is not present at this time. GO to E5.
E2 CHECK THE AIR BAG TONE WARNING INDICATOR CIRCUIT FOR GROUND SHORT
- Key in OFF position.
- Depower the system. refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING .
- Disconnect: RCM C310a.
- Disconnect: Instrument Cluster Module C220a.
- Measure the resistance between RCM C310a pin 22, circuit 1390 (DB), harness side and RCM C310a pin 16, circuit 649 (BK/OG), harness side.
  
  Fig 1: Checking Air Bag Tone Warning Indicator Circuit For Ground Short
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 1,000,000 ohms?
- Yes : GO to E3.
- No : REPAIR circuit 1390 (DB). GO to E6.
E3 CHECK THE AIR BAG TONE WARNING INDICATOR CIRCUIT FOR AN OPEN
- Measure the resistance between RCM C310a pin 22, circuit 1390 (DB), harness side and instrument cluster module C220a pin 13, circuit 1390 (DB), harness side.
  
  Fig 2: Checking Air Bag Tone Warning Indicator Circuit For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to E4.
- No : REPAIR circuit 1390 (DB). GO to E6.
E4 CHECK THE AIR BAG TONE WARNING INDICATOR
- Connect: Instrument Cluster Module C220a.
- Deactivate the system. refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEACTIVATION AND REACTIVATION .
- Key in ON position.
- Measure the voltage at RCM C310a pin 22, circuit 1390 (DB).
  
  Fig 3: Measuring Voltage Between RCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : INSTALL a new RCM. REFER to RESTRAINTS CONTROL MODULE (RCM) . GO to E6.
- No : INSTALL a new instrument cluster module. REFER to INSTRUMENT CLUSTER . GO to E6.
E5 CHECK FOR AN INTERMITTENT FAULT
- Key in OFF position.
- Enter the following diagnostic mode on the diagnostic tool: On-Demand Self Test.
- Was DTC B1892 retrieved during the on-demand self test?
- Yes : GO to E2.
- No : CHECK for causes of an intermittent short to ground or open on circuit 1390 (DB). ATTEMPT to recreate the hard fault by flexing the wire harness and cycling the ignition key frequently. REPAIR any intermittent concerns found. GO to E6.
E6 CHECK FOR ADDITIONAL DTCs
- Refer to the continuous DTCs recorded during Step E1.
- Were any continuous DTCs retrieved during Step E1?
- Yes : Do not clear any DTCs until all DTCs have been resolved. GO to the RESTRAINTS CONTROL MODULE (RCM) DIAGNOSTIC TROUBLE CODE (DTC) TABLE for pinpoint test direction.
- No : RECONNECT the system. If previously directed to deactivate the system, REACTIVATE the system. refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEACTIVATION AND REACTIVATION . REPOWER the system. refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING . PROVE OUT the system. CLEAR all DTCs.